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The following message was posted to: PharmPK
Dear All
We have developed and validated a method by lc-ms\ms. in this method
we found approximate 1% carryover. it could not be eliminated anyhow.
can anybody suggest in actual study sample analysis (statistical
analysis) how this can be justified. and what is the procedure for
statstical analyis in this situation.
thanks
Puran Singhal
Research Scientist
Ranbxy Research Laboratories
Gurgaon
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Puran,
If by "carryover" you mean that following an injection of a standard,
an injection of a blank gives a 1% peak, then there may be a hardware
solution to this. Ask the instrument vendor about other injectors and
techniques for rinsing the injector components after injections.
Regards,
Frank
Frank Bales, Ph.D.
Email: frankbales.aaa.msn.com
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Dear Puran,
I met the carry over problems when I was using GC-MS to develop a bio-assay.
Some suggestions:
1) Try to avoid highly concentrated samples
2) Clean the injection part and the ion source of your LC-MS system
3) Your LC column could also cause such problem; hence, you change to a new
column and try again
4) Inject some blank between each sample
Good luck!
Haishu Lin, PhD
Scientist
ProStrakan
102 Route de Noisy
Romainville 93230
France
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Just inject one blank sample between each real sample, the problem
can be solved.
Dan Lu
Division of Pharmaceutics
the Ohio State University
Columbus, Ohio 43210
614-292-4922
[I'm not sure about solved but a good diagnostic. I don't remember
the original question but careful consideration of the inject, rinse
cycle is important and blank sample or solvent between samples can be
instructive - db]
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The following message was posted to: PharmPK
Dear all,
An elegant way to solve the problem of carry-over is to inject a
blank extract. So if you re measuring in plasma: treat a blank plasma
sample as if it would be a sample and inject it. Repeat is necessary
and validate that it is sufficient.
Yours sincerely,
Rob ter Heine
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Dear puran
Even we face such problems in LC/MS/MS and it is difficulty to
justify, i feel you may check your rinsing solvent, if your compound
is acidic try to keep the rinsing in basic side, please make sure
that your column may stable at that pH.
guidelines suggests there is 20% responce of your LLOQ is allowed in
the blank plasma, even i have doubt if your carry over is less than
20% of your LLOQ, is it ok?
if still carry over is there hope we can use some 1 to 5% DMSO in
your rinsing solvent, i think this may be use for for you
Venkatesh
USM, MALAYSIA
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